Three new species of the crangonid genus Metacrangon Zarenkov (Crustacea: Decapoda: Caridea) from Australia

2010·6.8 MB·

by  Joanne Taylor

MemoirsofMuseumVictoria67:45-59(2010)
ISSN 1447-2546(Print) 1447-2554(On-line)
http://museumvictoria.com.au/About/Books-and-Journals/Journals/Memoirs-of-Museum-Victoria
Three new species ofthe crangonid genus Metacrangon Zarenkov (Crustacea:
Decapoda: Caridea) from Australia
TomoyukiKomai1 andJoanneTaylor2
1NaturalHistoryMuseumandInstitute,Chiba,955-2Aoba-cho,Chuo-ku,Chiba,260-8682Japan(komai@chiba-muse.
or.jp)
2MuseumVictoria,GPOBox666,Melbourne,Vic.3001,Australia([email protected])
Abstract Komai,T.&Taylor,J.2010.ThreenewspeciesofthecrangonidgenusMetacrangonZarenkov (Crustacea: Decapoda:
Caridea)fromAustralia.MemoirsofMuseumVictoria67:45-59.
ExaminationofcollectionsfromwatersoffsouthernAustraliaresultedinsignificantfindingsofthreenewspecies
ofthecrangonidgenusMetacrangonZarenkov, 1965:M.australissp.nov.fromtheSouthernOceanoffTasmania,west
ofMaquarieIsland;M.pooreisp.nov.fromtheTasmanSea;andM.spinidorsalissp.nov.fromwatersoffsouthwestern
WesternAustraliaandtheTasmanSea.Thetwoformerspecies aremorphologically similartoM.variabilis (Rathbun,
1902)fromthenorthPacificandM.proximaKim,2005fromJapan.ThethirdisreferredtotheinformalM.jacqueti(A.
Milne-Edwards,1881)speciesgroup.Differentiatingcharactersofthesethreenewspeciesarediscussedandakeytotheir
identificationisprovided.
Keywords Crustacea, Decapoda, Caridea, Crangonidae, Metacrangon new species, key, Australia, Victoria, Western Australia,
,
Tasmania,MacquarieIsland
Introduction continental shelfandslopeinAustralia’s southwestregion’).
The crangonid shrimp genusMetacrangonZarenkov, 1965 is This present study was initiated to describe the new
ratherdiverse,with26namedspeciesandone subspecies (De species from southwesternAustraliareported by Poore etal.
Grave et al., 2009; Komai and Komatsu, 2009; Komai, in (2008), but our examination of the Metacrangon specimens
press). It is characterised by the shallowly depressed gastric lodged in Museum Victoria, referred to by Poore (2004),
region of the carapace, the usual presence of a pair of confirmed two further species, both new to science. In this
submedian teeth on the carapace, the laterally flared pleuron paper, these three new species are described and illustrated:
ofthesixthabdominalsomite,andthesecondpleopodwithan M. australis sp. nov. from waters southeast of Tasmania off
appendix masculina being much shorter than the endopod Macquarie Island; M. spinidorsalis sp. nov. (- Metacrangon
(Zarenkov, 1965; Butler, 1980; KimandHayashi, 2003; Kim, sp.Poore, 2004andMetacrangon sp.MoV 5423 Poore etal.,
2005). Christoffersen (1988) supported the monophyly ofthe 2008) from southwesternAustralia and the Tasman Sea; and
genus. Many ofthese 27 taxa are rare, reportedfrom limited M.poorei sp. nov.fromthe Tasman Sea.These three species
geographic locations that are often confined to or near their occurinratherhighlatitudinalareas.
type localities. Although species of Metacrangon are well The examined material remains in Museum Victoria,
representedinthenorthPacificOcean,nospeciesofthegenus Melbourne (MV) andtheWesternAustralianMuseum, Perth
thhaavte ubneiednendteifsicerdibesdpefcrieosm Awuesrteralikan.oPwonorteo(2o0c0c4u)rreopnorttehde (WAM). The abbreviation ‘sp. MoV’ refers to the unique
southeasternshelfoffeasternTasmaniaataround500-600m Museum Victoria number allocated to new or undetermined
depth, but to date, these have remained undescribed. A taxa (and is not the same as sp. nov., which refers to a new
nominal new species from southwestern Australia was also species). The measurement provided is of the postorbital
recentlyreportedbyPooreetal.(2008)fromsamplingcruises carapace length (cl) measured fromthe level ofthe posterior
offthe continental margin ofWestern Australia onboard the margin of the orbit to the midpoint of the posterodorsal
FRVSouthernSurveyorin2005,mountedby CSIROMarine margin. In order to avoid unnecessary repetition, only M.
and Atmospheric Research (CMAR) and Museum Victoria spinidorsalis is fully described and differential descriptions
(project entitled ‘Mapping benthic ecosystems on the deep aregivenfortheothertwonew species.
46 T. Komai&J.Taylor
Taxonomicaccount
Metacrangonaustralissp.nov.
Figures 1-3
Material examined. Holotype: Australia, Tasmania, southwestern
PacificwestofMacquarieIsland(54°42.42'S,158°45.12'E-54°41.36'S,
158°43.12'E),700-900 m, 22-23 Jan 1999, FRVSouthernSurveyor
epibenthicsled(stnSS01/99/65),NMVJ60424(1female,cl13.1mm).,
Paratypes:samedataasholotype,NMVJ61200(2females,cl9.9,
12.1mm).
Description. Body (fig. 1) moderately robust. Rostrum (figs
2a-b) narrowly triangular with acute apex in dorsal view,
directedforwardorslightlyascending,about0.20timesaslong
as carapace; dorsal surfacewithmiddorsal carinainproximal
half; lateral margin slightly convex in lateral view, merging
into orbital margin; midventral carinadistinct, ventral margin
nearlystraightinlateralview.Carapace(figs 1,2a)veryslightly
widened anteriorly, longer than wide postorbitally; surface
covered with very short setae; dorsal midline with two
moderately small, subequal teeth; anterior (epigastric) tooth
arising at 0.10 of carapace length, posterior (cardiac) tooth
brokenoff,arisingat0.75-0.80ofcarapacelength; submedian
andhepaticteethmoderatelysmall;antennaltoothmoderately
strong, directed forward in dorsal view, weakly ascending
(same degree as rostrum) in lateral view, acuminate, falling
short of rostral tip; orbital cleft absent; anterolateral margin
betweenantennalandbranchiostegalteethsinuouswithobtuse
lobule (holotype) or with tiny denticle (paratypes) inferior to
baseofantennaltooth;branchiostegaltoothmoderatelystrong,
very slightly diverging anteriorly in dorsal view and strongly
ascending in lateral view, distinctly overreaching dorsodistal
margin of antennal basicerite; pterygostomial tooth small,
visible in lateral view; postorbital carina clearly delimited,
accompaniedbylongitudinal suture;weakepibranchial carina
present.
Thoracic sternites depressed; fifth sternite with small,
forwardlydirectedmediantooth,otherwiseunarmed.
Abdomen (figs 1, 2c) moderately sculptured; first to fifth
somites with sharply delimited, crested middorsal carina,
anterior end ofmiddorsal carina on second somite produced
anteriorly.Pleuronofanteriorfoursomitesroundedmarginally.
Fifth somite with posterodorsal margin slightly produced
medially; posterolateral margin unarmed; pleuron with
posteroventral angle rounded, ventral margin gently convex.
Sixthsomite 1.6timeslongerthanwide,withdistinct,slightly
curvedsubmediancarinae,notreachingposterodorsalmargin;
dorsolateralcarinadistinct,reachingtoposterodorsalmargin;
posterodorsal margin produced, distinctly bilobed; pleuron
flaredlaterally,withsmallposteroventraltooth;posterolateral
processmoderatelystrong,directedposteriorly,terminatingin
sharptooth.Telson(figs2c-d)taperingdistallytoacuteapex,
with three pairs of minute dorsolateral spines, anteriormost
pair located at posterior 0.35; three pairs of spiniform setae
posteriortothirdpairofdorsolateral spines.
Eye(figs2a-b)aslongaswide;corneaaswideaseyestalk, Figure 1. Metacrangon australis sp. nov., holotype, female (cl 13.1
darklypigmented,cornealwidth0.13-0.15ofcarapacelength; mm),NMVJ60424,entireanimalinlateralview(leftfifthpereopod
eyestalkwithsmall,papilla-likedorsaltubercle. lost).Scalebar=5mm.
ThreenewspeciesofthecrangonidgenusMetacrangonZarenkov(Crustacea: Decapoda:Caridea)fromAustralia 47
Figure2.Metacrangonaustralissp.nov.,holotype,female(cl 13.1mm),NMVJ60424:a,carapaceandcephalicappendages,dorsalview(setae
partiallyomitted);b,anteriorpartofcarapace(leftside)andleftcephalicappendages,dorsalview;c,abdomen,dorsalview;d,posteriorpartof
telson,dorsalview.Scalebars=5mmforaandc;2mmforb; 1 mmford.
48 T. Komai&J.Taylor
Figure3.Metacrangonaustralis sp.nov.,holotype,female(cl 13.1 mm),NMVJ60424: a,distaltwosegmentsofleftthirdmaxilliped,dorsal
(extensor)view(setaeomitted);b,distalpartofantepenultimatesegmentofleftthirdmaxilliped,ventralview;c,leftfirstpereopod,lateralview;
d, same, subchelaandcarpus,dorsal (extensor) view; e,leftsecondpereopod,lateralview;f,rightthirdpereopod,lateralview; g,leftfourth
pleefrteuorpoopdo,dlaalteerxalopvoide,w;dohr,ssaalmvei,edwac(tsyeltuaes,ofmlietxtoerd)v.ieSwc;ali,erbiagrhtsf=if2thmpemrefooproad-,glaatnedrail;v1iemwm;j,fosramhea,nddacj;ty0l.u5s,mfmlexfoorrvk.iew;k,posterolateraltoothof
ThreenewspeciesofthecrangonidgenusMetacrangonZarenkov(Crustacea: Decapoda:Caridea)fromAustralia 49
Antennularpeduncle(figs2a-b)moderatelystout,reaching sharp, crested middorsal carina; and the anteriorthree pleura
midlength of antennal scale. First segment with prominent, are rounded marginally. Of particular note is the lack of an
blunt distolateral process directed dorsally; distomesial orbital cleft, an uncommontraitpreviously known only inM.
margin unarmed; stylocerite falling far short of distolateral knoxi(Yaldwyn, 1960)(seeKomai, 1997).M.knoxiisreferred
process of first segment, terminating in slender, sharp tooth, to the M.jacqueti (A. Milne-Edwards, 1881) species group
lateral margin gently convex. Second segment widened (Komai, 1997) and is readily distinguishedfromM. australis
distally, slightly longer than wide, with prominent, blunt by the anteriormiddorsal tooth onthe carapace that arises at
distolateral process. Third segment much wider than long. themidlengthoftherostrumandthepresenceofaventraltooth
Outerflagellumconsistingof 13 articles. oneachfirsttothirdabdominalpleuron.
dorsAondtisetnanlallatbearsailcearnigtlee(afingdsl2oan-gb)vesnttoruotl,atweirtahlatcouottehlydipstoiinnctteldy Ealtlyumdoilnoggyto.thNeatmyepde lo‘caaulsittryaloifs’t,hiLsatnienw smpeeacnieisn,grep‘rsoeustehnetrinn’g,
overreaching dorsodistal lateral angle. Antennal scale (figs
thesouthernmostlocalityofthegenus.
2a-b)0.50-0.55timesaslongascarapaceandabout2.3times
longerthan wide; lateral margin weakly concave; distolateral
Metacrangonpooreisp.nov.
toothmoderatelybroad,slightlyoverreachingroundedlamella.
Third maxilliped (fig. 3a) relatively stout, overreaching Figures4,5
antennal scale by full length of ultimate segment; ultimate
Material examined. Holotype: Australia, off southeastern Victoria,
segmentabout4.5timeslongerthanwide;penultimatesegment (39°53.76'S, 149°03.39'E), 1608 m, 28 Apr 2000, FRV Southern
about 2.3 times longer than wide; antepenultimate segment Surveyor,epibenthicsled,(stnSS01/00/246),NMVJ52069(1female,
withtwosubequal spiniformsetaesubdistally(fig.3b). cl8.1mm).
First pereopod (fig. 3c) moderately stout, slightly
overreaching antennal scale; palm (fig. 3d) 2.9 times longer Description. Based on holotype female. Body (figs 4a-e)
than wide, not widened proximally or distally; lateral and moderately robust. Rostrum (figs 4a-b, 5a) triangular with
mesial marginsfaintly sinuous; thumb relatively long; carpus acute apex in dorsal view, strongly ascending (angle against
with small ventrolateral tooth, otherwise unarmed on horizontal plane ofcarapace about45°), 0.20times as long as
distolateral margin; merus with small dorsodistal tooth, carapace; dorsal surface with low, but clearly delimited
ventral margin sinuous, crested. Second pereopod with middorsalcarina;lateralmarginfaintlysinuousinlateralview,
dactylus about0.3 times aslong aspalm(fig.3e); lengthratio mergingintopostorbitalregionofcarapace; midventral carina
of chela to ischium 1:23:2.2:1.8. Third pereopod (fig. 3f) distinct, ventral margin sinuous inlateral view.Carapace (figs
slender; length ratio of dactylus to ischium 1:1.83.8:2.8:2.8. 4a-b) notwidenedposteriorly, longerthan wide postorbitally;
Fourth pereopod (fig. 3g) relatively stout, reaching nearly dorsal midline with two moderately small teeth; anterior
distal margin of antennal scale; dactylus (fig. 3H) elongate (epigastric) tooth arising at 0.18 of carapace length, posterior
subovate, spatulate, about 0.5 times as long as propodus, (cardiac) tooth broken off, arising at 0.68 of carapace length;
margins naked; dactylus-propodus articulation about 60°; submedianandhepaticteethmoderately small; antennaltooth
propodus about4.0times longerthanwide; propodus-carpus moderately strong, directed forward in dorsal view, strongly
combined distinctly shorter than merus-ischium combined. ascending(samedegreeasrostrum)inlateralview,acuminate,
Fifthpereopod(fig.3i) shorterthanfourthpereopod; dactylus falling slightly short of rostral apex; orbital cleft distinct;
anterolateral margin between antennal and branchiostegal
(fig. 3j) spatulate, subequal in length to dactylus of fourth
teeth concave, unarmed; branchiostegal tooth moderately
pereopod,about0.7timesaslongaspropodus.
Uropodal exopodwithbluntposterolateral tooth andwith strong, directedforward in dorsal view, strongly ascending in
threespiniformsetae(fig.3k). lateralview,reachingdorsodistalmarginofantennalbasicerite;
pterygostomial tooth small, clearly visible in lateral view;
Colouration.Notknown. postorbital carina clearly delimited, accompanied by
Distribution. Known only from the type locality in the longitudinal suture;epibranchialcarinaweaklyabsent.
Southern Ocean southeast of Tasmania, west of Macquarie Fifthtoeighththoracicsterniteseachwithdistinctmedian
Island,atdepthsof700-900m. keel: on fifth, spiniform, directed forward; on sixth,
terminating anteriorly in tiny tooth; on seventh, angulated
Remarks. Metacrangon australis is somewhat similar to M. anteriorly;andoneighth,rounded.
proxima, M. variabilis and M.poorei sp. nov. in the general Abdomen (figs 4c-e) slightly sculptured, surface sparsely
disposition of carapacial teeth and the carination of the punctate;firstsomitewithtraceofmiddorsalcarina,secondto
abdomen, butitis quiteuniquewithinthe genus inhavingthe fourth somites withratherbroad, clearly delimitedmiddorsal
combination of the following characters: the rostrum is carina. Pleuron of anteriorfour somites rounded marginally.
narrowly triangular and distinctly overreaches the distal Fifthsomitewithlow,ratherbroad,clearlydelimitedmiddorsal
cornealmargins;thecarapacehastwomiddorsalteeth,ofthem carina; posterodorsal margin faintly produced medially;
the anterior tooth is distinctly postrostral and the posterior posterolateral margin unarmed; pleuron with posteroventral
(cardiac) tooth arises at 0.75-0.80 ofthe carapace length; the anglerounded,ventralmargingentlyconvex.Sixthsomite 1.7
lateral margin ofthe rostrum merges into the orbital margin, times longer than wide, with distinct, slightly curved
thusnocleftisdefined;thefirsttofifthabdominalsomitesbear submedian carinae, not reaching posterodorsal margin;
50 T. Komai&J.Taylor
Figure4.Metacrangonpooreisp.nov.,holotype,female(cl8.1 mm),NMVJ52069: a,carapaceandcephalicappendages,dorsalview;b,same,
lateralview;c,firsttothirdabdominalsomites,dorsalview;d,fourthabdominalsomitetotelson,dorsalview;e,entireabdomen,lateralview.
Scalebar=2mm.
ThreenewspeciesofthecrangonidgenusMetacrangonZarenkov(Crustacea: Decapoda:Caridea)fromAustralia 51
Figure 5.Metacrangonpoorei sp. nov., holotype,female (cl 8.1 mm), NMVJ52069: a, anteriorpart ofcarapace (left side) andleft cephalic
appendages,dorsalview;b,distaltwosegmentsanddistalpartofantepenultimatesegmentofleftthirdmaxilliped,ventral(flexor)view;c,left
firstpereopod,lateralview;d,same,subchela,flexorview;e,leftsecondpereopod,lateralview;f,leftthirdpereopod,lateralview;g,leftfourth
vpieerwe.opSocda,lelabtaerrsal=vi1emw;mh,fosramae-,gdaancdtyil;u0s.,5fmlemxorfovriehw;ani,drji.ghtfifthpereopod,lateralview;j,posterolateraltoothoflefturopodalexopod,dorsal
52 T. Komai&J.Taylor
dorsolateralcarinadistinct,reachingtoposterodorsalmargin; distinguished from the latter two species by the following
posterodorsal margin produced, weakly bilobed; pleuron characters: the rostrum is acutely pointed and reaches to the
flared laterally, posteroventral tooth small; posterolateral distal corneal margins in M. poorei, whereas it is blunt or
process moderately strong, directed slightly laterally, subacute at the tip and falls far short of the distal corneal
terminating in sharptooth.Telson (fig.4d) damaged, butone marginsinthelattertwo species;theanterolateral angleofthe
pairofdorsolateral spines stillpreserved. postorbital carinaisroundedinM.poorei,ratherthanbearing
Eye (figs4a, 5a) slightlylongerthanwide; corneaas wide asmalltriangulartoothordenticleinthelattertwospecies;the
asproximalpartofeyestalk,darklypigmented, cornealwidth lateral carina on the fifth abdominal somite is obsolete inM.
0.17 of carapace length; eyestalk with small, papilladike pooreisp.nov,butitisdistinctinthelattertwospecies;andthe
dorsaltubercle. styloceriteofthe antennulereachesthe distolateral process on
Antennular peduncle (figs 4a, 5a) moderately stout. First the first peduncular segment in the new species, rather than
segment with prominent, blunt distolateral process directed fallingfarshortofitinthelattertwospecies.
dorsally; distomesial margin unarmed; stylocerite just
Etymology.Itisourpleasuretodedicatethisnewspeciestoour
reachingtipofdistolateralprocess,subacutelypointed,lateral
esteemedcolleague,Dr.GaryC.B.Poore.
margin gently convex. Second segment slightly widened
distally, distinctly longer than wide, with prominent, blunt
Metacrangonspinidorsalissp.nov.
distolateral process. Third segment wider than long. Outer
flagellumconsistingof10-11 articles. Metacrangonsp.(Poore,2004, 139,fig.36f)
Antennalbasicerite(fig.5a)stout,withroundeddorsodistal Metacrangonsp.MoV5423.(Pooreetal.,2008,81)
lateral angle and long ventrolateral tooth distinctly Figures6-10
overreaching dorsodistal lateral angle. Antennal scale
damaged(fig.5a). Materialexamined.Holotype:Australia,WesternAustralia,offPoint
Third maxilliped (fig. 5b) relatively slender, overreaching Hillier(35°22.54'S,117°12.25'E-35°22.54'S,117°12.25'E),539m,22
antennalscaleby0.6lengthofultimatesegment;ultimatesegment NWoAvM2005,FRVSouthernSurveyor,beamtrawl(stnSS10/2005/019),
graduallytaperingdistally,6.0timeslongerthanwide;penultimate ParCa4t5yp1e1s5:(1Tafsemmaanlie,a,clT1a0s.m4amnm)S.ea off Maria Island (42°42.8'S,
segment about 2.7 times longer than wide; antepenultimate 148°22.2'E),450m,25Jun 1984,RVSoela,demersalbeamtrawl(stn
segmentwithtwounequalspiniformsetaesubdistally. S03/84/77),NMVJ40886(1 female,cl7.6mm);SouthernOcean,48
First pereopod (figs 5c-d) moderately stout; palm 3.5 kmwestofRichardsonPoint(4P15.0'S, 144°08.0'E), 520m, 20 Oct
times longer than wide, not widened proximally or distally; 1984,FrankandBrycedemersaltrawl(stnS05/84/51),NMVJ40954
lateral andmesial marginsfaintly sinuous;thumbmoderately (1female,cl9.0mm).WesternAustralia,offPointHillier(35°22.54'S,
broad; carpus with small ventrolateral tooth, otherwise 117°12.25'E -35°22.54'S, 117°12.25'E), 539 m, 22 Nov 2005, FRV
unarmed on lateral margin; merus with small dorsodistal SouthernSurveyor,beamtrawl(stnSS10/2005/019),NMVJ54497(3
tooth, ventral margin sinuous, crested. Second pereopod (fig. females, cl 5.4-10.4 mm, 6 males, cl 6.1-7.0 mm); off Bald Island
5oef)cwhietlhadatcotyilsucshaibuomut1:01..57:t1i.6m:e1s.5a.sTlhoinrgdasppearlemo;poldeng(tfihg.ra5tfi)o N((33o55v°°01422..0040195''SS,,(st11n1188S°°S331990../502040''0EE5/--0333255)°°,1123N..14M40''VSS,,J111119882°°144500..0(3180''fEEe))m,,a4l7e32,18--c4l701780.7mmm,,m)22;34
slender; length ratio of dactylus to ischium 1:1.9:3.4:2.5:2.6. Nov 2005(stnSS10/2005/034),WAMC45116(1 female,cl 6.9mm);
Fourth pereopod (fig. 5g) moderately stout; dactylus (fig. 5h) offPerthCanyon(31°59.33'N,115o10.59'E-32°00.07'S,115°10.4rE),
narrowly spatulate, about 0.6 times as long as propodus, 508-478 m, 29 Nov 2005 (stn SS10/2005/068), NMV J54512 (4
margins naked; dactylus-propodus articulation about 30°; femalescl67-9.5mm, 1 malecl6.5mm).
propodus about 5.0 times longer than wide; carpus shorter
than propodus, with numerous long setae on dorsal margin; Description.Female.Body(fig.6)moderatelyrobust.Rostrum
row oflong setae ondorsal andventral margins ofmerus and (figs7a-b) narrowlytriangularwithacute apexindorsalview,
directedforward, 0.20-0.25 times as long as carapace; dorsal
ischium(dorsalsetaelongerthanventralsetae).Fifthpereopod
(fig.5i)slightlyshorterthanfourthpereopod;dactylusslender, surface nearly flat; lateral margin slightly arched in lateral
view, merging into postorbital region ofcarapace; midventral
subspatulate, longer than dactylus offourth pereopod, about
carina low, ventral margin slightly sinuous in lateral view.
0.8timesaslongaspropodus.
Uropodalexopodwithminuteposterolateraltoothandminute Carapace (figs 6, 7a) slightly widened posteriorly, slightly
longerthanwidepostorbitally;surfacecoveredwithveryshort
spinulejustlocatedmesialtoposterolateraltooth(Fig.5j).
setae;dorsalmidlinewithtwomoderatelysmallteeth;anterior
Colouration.Notknown. tooth arising atrostral base, not overlapping rostrum, slightly
Distribution. Known only from the type locality off largerthan posterior (cardiac) tooth; posterior (cardiac) tooth
arising at 0.55-0.60 of carapace length; submedian teeth
southeasternVictoria,atadepthof1608m.
moderatelysmall;hepatictoothrelativelysmall;antennaltooth
Remarks.Metacrangonpooreisp.nov.ismorphologicallyvery moderately strong, directedforwardin dorsal view, somewhat
similartoM.variabilis(Rathbun, 1902)fromthenortheastern ascending in lateral view (angle about 30° against horizontal
PacificandM.proximoKim,2005fromJapaninthedisposition planeofcarapace),acuminate,farfallingshortofrostralapex;
ofteethonthecarapaceandthedevelopmentofthemiddorsal orbital cleft present, but only weakly delimited; anterolateral
carinaoftheabdomen.Nevertheless,thenew speciesis easily margin between antennal and branchiostegal tooth concave,
ThreenewspeciesofthecrangonidgenusMetacrangonZarenkov(Crustacea: Decapoda: Caridea)fromAustralia 53
with tiny spinule inferior to base of antennal tooth;
branchiostegal tooth moderately strong, directed forward in
dorsal view and somewhat dorsally in lateral view, reaching
dorsodistalmarginofantennalbasicerite;pterygostomialtooth
small, not visible in lateral view; postorbital carina clearly
delimited, accompanied by longitudinal suture; epibranchial
carinaweaklydelimited.
In spawning molts, thoracic sternum concave, armature
absent; only fifth sternite with small tubercles medially. In
nonspawningmolts,fifthsternitewithsharp,procurvedtooth;
sixth to seventh somites each with rounded, strongly
compressedprominence,becominghigherposteriorly.
Abdomen (figs 6, 7c) slightly sculptured; anterior two
somiteswithouttraceofmiddorsalcarinaanteriorly,butsecond
tergum with distinct spiniform middorsal tooth located at
anterior end of posterior section; third somite with trace of
middorsalcarina,andfourthsomitewithbroad,clearlydelimited
middorsal carina.Firstand secondpleuraeachwithblunttooth
onventralmargin;thirdpleuronwithblunttoothatanteroventral
angle; fourth pleuron unarmed. Fifth somite with low, but
distinctmiddorsalcarina;posterodorsalmarginfaintlyproduced
medially; posterolateral margin unarmed; pleuron with
posteroventral angle subacutely pointed, ventral margin gently
convex. Sixth somite withdistinct, straightsubmediancarinae,
notreaching posterodorsal margin; dorsolateral carinadistinct,
reaching to posterodorsal margin; posterodorsal margin
produced,faintlybilobed;pleuronflaredlaterally,posteroventral
tooth small, acute or subacute; posterolateral process strong,
directedslightlylaterally,terminatinginsharptooth.Telson(fig.
7c)longerthansixthsomite,taperingtoacutetip;dorsalsurface
deeply grooved mesially, with three pairs of lateral spines,
anterior-most pair located at about midlength; two plumose
setaeposteriortothirdpairoflateralspines(fig.7d).
In spawning molt, first to fourth abdominal sternites
unarmed; fifth sternite with low median tubercle. Sixth
abdominal sterniteshallowdepressedmedially.
Eye (figs 7a-b) slightly longer than wide; cornea slightly
wider than eyestalk, light brown or opaque in preservative,
corneal width 0.14-0.15 of carapace length; eyestalk with
small,papilla-likedorsaltubercle.
Antennular peduncle (figs 7a-b) moderately stout,
overreaching midlength ofantennal scale. First segmentwith
prominent, blunt distolateral process directed dorsally;
distomesial marginunarmed; styloceritefalling slightly short
of distolateral process, acutely or subacutely pointed, lateral
margin gently convex. Second segment slightly widened
distally, distinctly longer than wide, with prominent, blunt
distolateral process. Third segment wider than long. Outer
flagellum overreaching distal margin of lamella of antennal
scalebyabout0.4length,consistingof10-11 articles.
Antennal basicerite (fig. 7e) stout, with sharply pointed
dorsodistal lateral angle and shortventrolateral tooth slightly
overreaching dorsodistal lateral angle; carpocerite
subcylindrical,reachingdistal0.20ofantennalscale.Antennal
scale(figs7a,7e) about0.50timesaslongascarapaceand2.3
times longer than wide; lateral margin faintly sinuous;
distolateral tooth relatively wide, slightly falling short of Figure 6. Metacrangon spinidorsalis sp. nov., holotype, female (cl
roundeddistalmarginoflamella. 10.4mm),WAMC45115,entireanimalinlateralview.Scalebar=5mm.
54 T. Komai&J.Taylor
WAM
Figure7.Metacrangonspinidorsalissp.nov.,holotype,female(cl 10.4mm), C45115: a,carapaceandcephalicappendages,dorsalview;
b,anteriorpartofcarapace(leftside),lefteyeandleftantennule,dorsalview(setaeomitted);c,abdomen,dorsalview;d,distalpartoftelson,
dorsalview;e,leftantennalscale,dorsalview.Scalebars=5mmforaandc;2mmforbande; 1mmford.